# Copyright (c) 2019 Ultimaker B.V.
# Cura is released under the terms of the LGPLv3 or higher.

import json
import webbrowser
from datetime import datetime, timedelta
from typing import Optional, TYPE_CHECKING
from urllib.parse import urlencode
import requests.exceptions


from UM.Logger import Logger
from UM.Signal import Signal

from cura.OAuth2.LocalAuthorizationServer import LocalAuthorizationServer
from cura.OAuth2.AuthorizationHelpers import AuthorizationHelpers, TOKEN_TIMESTAMP_FORMAT
from cura.OAuth2.Models import AuthenticationResponse

if TYPE_CHECKING:
    from cura.OAuth2.Models import UserProfile, OAuth2Settings
    from UM.Preferences import Preferences


##  The authorization service is responsible for handling the login flow,
#   storing user credentials and providing account information.
class AuthorizationService:
    # Emit signal when authentication is completed.
    onAuthStateChanged = Signal()

    # Emit signal when authentication failed.
    onAuthenticationError = Signal()

    def __init__(self, settings: "OAuth2Settings", preferences: Optional["Preferences"] = None) -> None:
        self._settings = settings
        self._auth_helpers = AuthorizationHelpers(settings)
        self._auth_url = "{}/authorize".format(self._settings.OAUTH_SERVER_URL)
        self._auth_data = None  # type: Optional[AuthenticationResponse]
        self._user_profile = None  # type: Optional["UserProfile"]
        self._preferences = preferences
        self._server = LocalAuthorizationServer(self._auth_helpers, self._onAuthStateChanged, daemon=True)

    def initialize(self, preferences: Optional["Preferences"] = None) -> None:
        if preferences is not None:
            self._preferences = preferences
        if self._preferences:
            self._preferences.addPreference(self._settings.AUTH_DATA_PREFERENCE_KEY, "{}")

    ##  Get the user profile as obtained from the JWT (JSON Web Token).
    #   If the JWT is not yet parsed, calling this will take care of that.
    #   \return UserProfile if a user is logged in, None otherwise.
    #   \sa _parseJWT
    def getUserProfile(self) -> Optional["UserProfile"]:
        if not self._user_profile:
            # If no user profile was stored locally, we try to get it from JWT.
            try:
                self._user_profile = self._parseJWT()
            except requests.exceptions.ConnectionError:
                # Unable to get connection, can't login.
                return None

        if not self._user_profile and self._auth_data:
            # If there is still no user profile from the JWT, we have to log in again.
            Logger.log("w", "The user profile could not be loaded. The user must log in again!")
            self.deleteAuthData()
            return None

        return self._user_profile

    ##  Tries to parse the JWT (JSON Web Token) data, which it does if all the needed data is there.
    #   \return UserProfile if it was able to parse, None otherwise.
    def _parseJWT(self) -> Optional["UserProfile"]:
        if not self._auth_data or self._auth_data.access_token is None:
            # If no auth data exists, we should always log in again.
            return None
        user_data = self._auth_helpers.parseJWT(self._auth_data.access_token)
        if user_data:
            # If the profile was found, we return it immediately.
            return user_data
        # The JWT was expired or invalid and we should request a new one.
        if self._auth_data.refresh_token is None:
            return None
        self._auth_data = self._auth_helpers.getAccessTokenUsingRefreshToken(self._auth_data.refresh_token)
        if not self._auth_data or self._auth_data.access_token is None:
            # The token could not be refreshed using the refresh token. We should login again.
            return None

        return self._auth_helpers.parseJWT(self._auth_data.access_token)

    ##  Get the access token as provided by the repsonse data.
    def getAccessToken(self) -> Optional[str]:
        if self._auth_data is None:
            Logger.log("d", "No auth data to retrieve the access_token from")
            return None

        # Check if the current access token is expired and refresh it if that is the case.
        # We have a fallback on a date far in the past for currently stored auth data in cura.cfg.
        received_at = datetime.strptime(self._auth_data.received_at, TOKEN_TIMESTAMP_FORMAT) \
            if self._auth_data.received_at else datetime(2000, 1, 1)
        expiry_date = received_at + timedelta(seconds = float(self._auth_data.expires_in or 0))
        if datetime.now() > expiry_date:
            self.refreshAccessToken()

        return self._auth_data.access_token if self._auth_data else None

    ##  Try to refresh the access token. This should be used when it has expired.
    def refreshAccessToken(self) -> None:
        if self._auth_data is None or self._auth_data.refresh_token is None:
            Logger.log("w", "Unable to refresh access token, since there is no refresh token.")
            return
        self._storeAuthData(self._auth_helpers.getAccessTokenUsingRefreshToken(self._auth_data.refresh_token))
        self.onAuthStateChanged.emit(logged_in = True)

    ##  Delete the authentication data that we have stored locally (eg; logout)
    def deleteAuthData(self) -> None:
        if self._auth_data is not None:
            self._storeAuthData()
            self.onAuthStateChanged.emit(logged_in = False)

    ##  Start the flow to become authenticated. This will start a new webbrowser tap, prompting the user to login.
    def startAuthorizationFlow(self) -> None:
        Logger.log("d", "Starting new OAuth2 flow...")

        # Create the tokens needed for the code challenge (PKCE) extension for OAuth2.
        # This is needed because the CuraDrivePlugin is a untrusted (open source) client.
        # More details can be found at https://tools.ietf.org/html/rfc7636.
        verification_code = self._auth_helpers.generateVerificationCode()
        challenge_code = self._auth_helpers.generateVerificationCodeChallenge(verification_code)

        # Create the query string needed for the OAuth2 flow.
        query_string = urlencode({
            "client_id": self._settings.CLIENT_ID,
            "redirect_uri": self._settings.CALLBACK_URL,
            "scope": self._settings.CLIENT_SCOPES,
            "response_type": "code",
            "state": "(.Y.)",
            "code_challenge": challenge_code,
            "code_challenge_method": "S512"
        })

        # Open the authorization page in a new browser window.
        webbrowser.open_new("{}?{}".format(self._auth_url, query_string))

        # Start a local web server to receive the callback URL on.
        self._server.start(verification_code)

    ##  Callback method for the authentication flow.
    def _onAuthStateChanged(self, auth_response: AuthenticationResponse) -> None:
        if auth_response.success:
            self._storeAuthData(auth_response)
            self.onAuthStateChanged.emit(logged_in = True)
        else:
            self.onAuthenticationError.emit(logged_in = False, error_message = auth_response.err_message)
        self._server.stop()  # Stop the web server at all times.

    ##  Load authentication data from preferences.
    def loadAuthDataFromPreferences(self) -> None:
        if self._preferences is None:
            Logger.log("e", "Unable to load authentication data, since no preference has been set!")
            return
        try:
            preferences_data = json.loads(self._preferences.getValue(self._settings.AUTH_DATA_PREFERENCE_KEY))
            if preferences_data:
                self._auth_data = AuthenticationResponse(**preferences_data)
                self.onAuthStateChanged.emit(logged_in = True)
        except ValueError:
            Logger.logException("w", "Could not load auth data from preferences")

    ##  Store authentication data in preferences.
    def _storeAuthData(self, auth_data: Optional[AuthenticationResponse] = None) -> None:
        if self._preferences is None:
            Logger.log("e", "Unable to save authentication data, since no preference has been set!")
            return
        
        self._auth_data = auth_data
        if auth_data:
            self._user_profile = self.getUserProfile()
            self._preferences.setValue(self._settings.AUTH_DATA_PREFERENCE_KEY, json.dumps(vars(auth_data)))
        else:
            self._user_profile = None
            self._preferences.resetPreference(self._settings.AUTH_DATA_PREFERENCE_KEY)
